Employee Benefit Plans (Additional Information) (Detail) $ in Millions		1 Months Ended			3 Months Ended								6 Months Ended		9 Months Ended			12 Months Ended
	Oct. 01, 2016 USD ($)	Jan. 31, 2018 USD ($)	Oct. 31, 2016 USD ($)	Aug. 31, 2016 USD ($) purchase_agreement insurance_company retiree	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($) plan	Dec. 31, 2015 USD ($)	Jul. 31, 2016
Pension and Other Postretirement Benefits Disclosure [Line Items]
Pension settlement charge					$ 38	$ 0	$ 0	$ 22	$ 0	$ 968	$ 0	$ 0	$ 22	$ 0	$ 22	$ 968			$ 60	$ 968	$ 0
Discount rate used to calculate benefit obligation					3.20%				3.70%										3.20%	3.70%
ABO for all defined benefit pension plans					$ 3,382				$ 3,171										$ 3,382	$ 3,171
Net actuarial loss (gain) arising during the year																			$ 3
Return on plan assets assumption																			5.40%	6.10%	6.10%
Impact on net periodic pension expense																			$ 11
Weighted-average healthcare cost trend rate assumed for next fiscal year					6.10%														6.10%
Assumed ultimate health care cost trend rate					4.50%														4.50%
Assumed year that ultimate health care cost trend rate will be reached																			2024
Recognized expense for defined contribution pension plans																			$ 57	$ 70	$ 60
Defined contribution plan contribution rates as percentage of employee earnings																			6.00%
Company-matching contribution, percent of match																			100.00%
Compensation expense related to the ESOP																			$ 46	48	44
Deductible dividends on PPG shares held by the ESOP																			14	14	13
Expense (income) of the deferred compensation plan																			19	7	5
Increase (Decrease) in fair value of investments																			18	5	3
Obligations under the deferred compensation plan					$ 121				124										121	124
Investments in marketable securities by the deferred compensation plan					83				82										83	82
Aggregate PBO for the pension plans with PBO in excess of plan assets					2,544				2,406										2,544	2,406
Aggregate fair value of plan assets for the pension plans with PBO in excess of plan assets					1,792				1,609										1,792	1,609
Aggregate ABO for the pension plans with ABO in excess of plan assets					2,434				2,302										2,434	2,302
Fair value of plan assets for the pension plans with ABO in excess of plan assets					1,749				1,575										1,749	1,575
Pittsburgh Glass Works L L C
Pension and Other Postretirement Benefits Disclosure [Line Items]
Liabilities for pension and post-employment benefits earned for service up to the time of sale					369				342										369	342
Costs related to the pension and other postemployment benefit liabilities of the divested business																			$ 2	20	17
Minimum
Pension and Other Postretirement Benefits Disclosure [Line Items]
Company-matching contribution																			2.00%
Maximum
Pension and Other Postretirement Benefits Disclosure [Line Items]
Company-matching contribution																			5.00%
Pensions
Pension and Other Postretirement Benefits Disclosure [Line Items]
Contributions to defined benefit pension plans																			$ 87	204
Pension assets transferred																			0	(3)
Plan settlements																			95	2,338
Net actuarial loss (gain) arising during the year																			38
Estimated amounts of accumulated net actuarial loss that will be amortized from AOCI into net periodic benefit cost in 2012					68														68
Impact on net periodic pension expense																			22
Benefits paid																			167	233
Estimated future benefit payments in 2018					147														147
Estimated future benefit payments in 2019					147														147
Estimated future benefit payments in 2020					156														156
Estimated future benefit payments in 2021					161														161
Estimated future benefit payments in 2022					166														166
Estimated aggregate future benefits payments for the five years thereafter					901														901
Postretirement Health Coverage
Pension and Other Postretirement Benefits Disclosure [Line Items]
Increase (decrease) in benefit obligation due to U.S. Plan Merger and Remeasurement				$ (306)
Amortization reduction period				5 years 7 months 6 days
Other Postretirement Benefits
Pension and Other Postretirement Benefits Disclosure [Line Items]
Net actuarial loss (gain) arising during the year																			(35)
Estimated amounts of accumulated net actuarial loss that will be amortized from AOCI into net periodic benefit cost in 2012					17														17
Estimated amounts of accumulated prior service cost that will be amortized from AOCI into net periodic benefit cost in 2012					(60)														(60)
Impact on net periodic pension expense																			26
Benefits paid																			48	53
Estimated future benefit payments in 2018					54														54
Estimated future benefit payments in 2019					54														54
Estimated future benefit payments in 2020					53														53
Estimated future benefit payments in 2021					53														53
Estimated future benefit payments in 2022					52														52
Estimated aggregate future benefits payments for the five years thereafter					$ 231														$ 231
Flat Glass Business
Pension and Other Postretirement Benefits Disclosure [Line Items]
Settlement charge																				11
Flat Glass Business | Pensions
Pension and Other Postretirement Benefits Disclosure [Line Items]
Increase (decrease) in benefit obligation due to settlements																				(100)
Pension assets transferred																				55
European Fiber Glass
Pension and Other Postretirement Benefits Disclosure [Line Items]
Pension settlement charge			$ 46
Settlement charge																				46
European Fiber Glass | Pensions
Pension and Other Postretirement Benefits Disclosure [Line Items]
Increase (decrease) in benefit obligation due to settlements	$ (340)
Pension assets transferred																				250
United States, Canada, Netherlands and United Kingdom
Pension and Other Postretirement Benefits Disclosure [Line Items]
Percentage of defined benefit pension plan assets market value					93.00%														93.00%
Scenario, Forecast
Pension and Other Postretirement Benefits Disclosure [Line Items]
Weighted-average healthcare cost trend rate assumed for next fiscal year																		5.80%
Assumed ultimate health care cost trend rate																		4.50%
Scenario, Forecast | Flat Glass Business | Pensions | Minimum
Pension and Other Postretirement Benefits Disclosure [Line Items]
Pension assets transferred																		$ 5
Scenario, Forecast | Flat Glass Business | Pensions | Maximum
Pension and Other Postretirement Benefits Disclosure [Line Items]
Pension assets transferred																		$ 10
UNITED STATES
Pension and Other Postretirement Benefits Disclosure [Line Items]
Number of definitive purchase agreements | purchase_agreement				2
Number of insurance companies to service future benefit obligations | insurance_company				2
Number of Company's retirees affected by annuity purchase | retiree				13,200
Increase (decrease) in benefit obligation due to settlements																			$ (1,600)
Noncash Pension Settlement Charge - after tax																			535
Pension settlement charge																			857
Contributions to defined benefit pension plans																			$ 54	134	$ 224
Discount rate used to calculate benefit obligation																					4.50%	3.60%
Increase (decrease) in benefit obligation due to U.S. Plan Merger and Remeasurement																				306
Increase (decrease) in pension expense																				10
Return on plan assets assumption																			7.50%
UNITED STATES | Glass Segment
Pension and Other Postretirement Benefits Disclosure [Line Items]
Contributions to defined benefit pension plans																				12	$ 26
UNITED STATES | Scenario, Forecast
Pension and Other Postretirement Benefits Disclosure [Line Items]
Return on plan assets assumption																		7.40%
Foreign Plan
Pension and Other Postretirement Benefits Disclosure [Line Items]
Noncash Pension Settlement Charge - after tax																				47
Pension settlement charge																				64
Contributions to defined benefit pension plans																			$ 33	54	$ 39
Increase (decrease) in benefit obligation due to U.S. Plan Merger and Remeasurement																				$ (200)
Estimated future mandatory contributions, low end of range					$ 20														20
Estimated future mandatory contributions, high end of range					$ 30														30
Number of legacy plan windups | plan																				2
After-tax wind-up charges																				$ (34)
Pre-tax gain (loss) due to settlements																	$ (7)			(47)
Foreign Plan | Canada
Pension and Other Postretirement Benefits Disclosure [Line Items]
Contributions to defined benefit pension plans																				7
Defined Benefit Plan, Plan Assets, Contributions by Employer, Windup																				1
Foreign Plan | Glass Segment
Pension and Other Postretirement Benefits Disclosure [Line Items]
Contributions to defined benefit pension plans																				4
Foreign Plan | Scenario, Forecast
Pension and Other Postretirement Benefits Disclosure [Line Items]
Return on plan assets assumption																		5.30%
Retained U.S. Pension Plans
Pension and Other Postretirement Benefits Disclosure [Line Items]
Contributions to defined benefit pension plans																			$ 29	146
Welfare Benefits - U.S. and Canada
Pension and Other Postretirement Benefits Disclosure [Line Items]
Percentage of defined benefit pension plan assets market value					85.00%														85.00%
U.S. Qualified Pension Plan
Pension and Other Postretirement Benefits Disclosure [Line Items]
Noncash Pension Settlement Charge - after tax																			$ 22
Pension settlement charge																			35
Benefits paid																			87
U.S. Non-qualified Plan
Pension and Other Postretirement Benefits Disclosure [Line Items]
Noncash Pension Settlement Charge - after tax																			14
Cash payment to retirees - U.S. Non-qualified Pension Plan																			40
Pension settlement charge																			22
Defined Contribution Plan [Member]
Pension and Other Postretirement Benefits Disclosure [Line Items]
Accrued pensions					$ 15				$ 11										$ 15	$ 11
Subsequent Event
Pension and Other Postretirement Benefits Disclosure [Line Items]
Contributions to defined benefit pension plans		$ 25